The Farmland Bird Indicator
Farmland birds are used as an indicator of the general quality of the farmed environment because birds sit near the top of the food chain and trends have been well monitored by the British Trust for Ornithology since 1967.
UK Farmland Bird Indicator (1970-2007)
The UK Government has a commitment to reverse the long-term decline in the number of farmland birds. The UK Farmland Bird Indicator is made up of 19 species that are dependent on farmland, and not able to thrive in other habitats.
The graph opposite shows an index based on the combined population trends of the 19 farmland bird species on the UK farmland bird indicator.
The steepest declines occurred between the mid-1970s and the mid-1980s, with a more shallow decline since then. Of the 19 species on the indicator, 12 have declined over this period, six have increased, and one has roughly remained stable.
The turtle dove, grey partridge, corn bunting and tree sparrow have declined by more than 80 per cent - woodpigeon and jackdaw have increased by more than 100 per cent.
The overall average change for the 19 species is a 48 per cent decline since 1970. If you wish to see the population trend information for any common bird species in the UK, visit the BTO website.
Population trends results
Population trends for the 19 species on the UK Farmland Bird Indicator 1970-2007, showing species and percentage change.
Tree sparrow -94%
Corn bunting -90%
Turtle dove -89%
Grey partridge -87%
Yellow wagtail -73%
Reed bunting -27%
Stock dove +55%
Frequently asked questions
How is the indicator calculated?
The Common Bird Census (CBC) monitored all common breeding birds on chosen plots between 1966 and 2000. The Breeding Bird Survey (BBS) started in 1994 as a more straightforward survey that would attract a greater number of volunteers to participate across the UK and has been used to the present day. Both ran in parallel for six years to ensure the new scheme gave compatible results.
In the BBS, volunteer birdwatchers are given a random one-kilometre square from the national grid. They walk two one-kilometre transects and record all birds seen and heard on two visits between April and mid-June. There are currently more than 3,000 squares covered annually.
Trends in bird numbers through time are calculated from the combined records of the CBC and the BBS. The Farmland Bird Indicator is calculated by combining the individual bird trends into one average index.
Why are only these 19 species used?
In 1993, the British Trust for Ornithology categorised all the common breeding birds in Britain and Ireland by the habitat on which they are dependent. Species which commonly occupy more than one habitat were put in a generalist category.
The farmland category consists of 'species feeding in open farmland during the breeding season, even though they may nest in woods and hedges'. It included 28 species - six are too rare to be monitored by the BBS and two are introduced species which do not naturally occur in the UK and so were excluded. One (the barn owl) is nocturnal and is therefore also not well monitored by the BBS, or any other existing survey.
When the Farmland Bird Indicator was devised in 1999, Defra chose to use the remaining 19 species, for which annual population trends can be estimated, to calculate the annual average index.
Why are winter birds not included?
Sometimes you see more birds on farmland in winter than you do in summer. This is partially because birds aggregate into large flocks in the winter, which are more noticeable than when they are scattered across the farmland. Also, many species move to Britain from northern Europe to avoid the harsher winter weather on the continent.
Numbers seen on farmland in the winter are therefore very variable, often more a reflection on breeding success outside of the UK. Breeding population counts are a much more reliable means of monitoring population changes.